Method of retarding disintegration of fire-brick and product thereof



United States Patent METHOD OF RETARDING DISINTEGRATION OF FIRE-BRICKAND PRODUCT THEREOF James A. Shea, Gary, Ind., assignor to United StatesSteel Corporation, a corporation of New Jersey No Drawing. Originalapplication December 8, 1950,

Serial No. 199,911. Divided and this application October 17, 1951,Serial No. 251,827

1 Claim. (Cl. 25155.5)

This invention relates to the treatment of refractory material used forfurnace linings to retard disintegration thereof and, in particular, tothe treatment of fire-brick such as used in constructing the lining of ablast furnace, and the product resulting therefrom.

This is a division from my application Serial No. 199,911, filedDecember 8, 1950.

The lining of a blast furnace serves two principal purposes, viz., itresists the abrasion resulting from the descent of the burden throughthe stack and insulates the steel shell from the heat generated withinthe stack. Linings as now constructed are quite adequate in respect tothe first of these. The limit upon the length of a furnace campaign,however, is the tendency of the brick of which the lining is constructedto disintegrate in a zone intermediate the interior and exterior of thelining, in which the temperature ranges between certain well definedlimits (800-1200" F.). This disintegration is believed to result fromthe reaction of carbon monoxide coming in contact with the iron oxidecontent of the fire clay of which the brick are composed (The Making,Shaping and Treating of Stee Camp and Francis, th edition, 1940,published by the assignee hereof, page 248).

Many proposals have been made to prevent disintegration of fire-bricklinings but none of them has afforded a satisfactory solution of theproblem so far as I am aware. One of them is to employ during firing, atemperature sufficiently high to produce hard-burned brick. Another isto limit the thickness of the lining and make special provisions forcooling the exterior (op. cit., idem loc.). Both these proposalsincrease the cost.

I have invented a novel method of treating fire-brick to prolong itslife and the resulting product which exhibits remarkable resistance todisintegration. From another viewpoint, I have discovered that a liningof fire-brick may be given a useful life much longer than that possibleheretofore under similar conditions, simply by subjecting the brickafter firing to contact with certain compounds under conditions favoringabsorption thereof or reaction therewith. I have also discovered severalclasses of compounds, each class including two or more specificcompounds, which are capable of imparting this quality to ordinaryfire-brick. These classes are (l) sulphuric acid, metallic salts thereofand other compounds containing the sulphate radical; (2) certain saltsof sulphurous acid; (3) certain sulphides; (4) certain thiocyanates; and(5) numerous metallic chlorides.

The mode of applying the reagent selected varies with the naturethereof. Sulphuric acid and its salts, preferably used as aqueoussolutions of suitable concentration, and the compounds which arenormally liquid, are applied by dipping or spraying the brick, pouringthe solution over the brick or mixing with the mortar used in laying thebrick. The compounds which are normally gaseous are applied bysubjecting the brick to contact with the gases while heated to asuitable temperature favoring absorption of the gases by the brick. Thesolid .KW t/ 2,724,887 Patented Nov. 29, 1955 sulphates and chloridesmay be vaporized or decomposed and applied similarly. Solid and liquidcompounds may be also applied by sprinking them on the brick or bydiffusing the vapor or decomposition products thereof into theinterstices of the brick. The quantity of the reagent actually taken upby the brick need be only a very minute amount, varying from a trace toan amount which is barely measurable, although this amount will varywith the nature of the reagent and the manner in which it is applied.

The reasons for the retardation of disintegration of the brick treatedaccording to the invention are not clear. It is believed, however, thatthe reagent applied somehow has the effect of rendering the iron oxidepresent in fire clay incapable of acting as a catalyst for thecarbon-forming reaction of carbon monoxide. In other words, it acts as acatalyst poison or inactivator thus preventing the carbon monoxideabsorbed by the brick from being converted to molecular carbon andcarbon dioxide.

Fire-brick to be treated by my invention are made from fire clay in theknown manner. After being fired and cooled, they are brought intocontact with the selected reagent, the exact procedure depending on theparticular reagent.

Among the various classes of reagents which I have found satisfactoryfor treating brick according to the invention are those having thesulphate (S04) radical. These include sulphuric acid, the sulphates ofammonium, aluminum, cobalt and manganese, ethyl sulphate and ammoniumpersulphate. The acid is preferably applied by dipping the brick in orspraying them with sulphuric acid of from 10 to 50% concentration. Theinorganic salts are applied by dipping the brick in or spraying themwith an aqueous solution of from 10 to 30% concentration. Ethyl sulphatemay be used full strength. 7

Another group of reagents which may be used successfully are sulphitesincluding sodium sulphite, sodium acid sulphite and ammonium sulphite.These salts are applied in the manner explained above.

Several sulphides are also capable of imparting the desired resistanceto disintegration. They are hydrogen sulphide, ammonium sulphide andcarbon disulphide. The latter being a liquid may be sprayed or sprinkledon the brick. The two former being gaseous are brought into contact withbrick heated to a temperature of from 500 to 2000" F., for a period ofabout a half-hour, and the vapor of carbon disulphide may be similarlyapplied. Specifically the brick may be treated with hydrogen sulphideand carbon disulphide by releasing these vapors in a periodic kilncontaining the brick during the cooling period after firing, when thebrick are between 700 and 1500 F.

Thiocyanates are another group of salts which may be used in aqueoussolution as explained above, among them potassium, sodium, and ammoniumthiocyanates. Thiosulphates may also be employed, e. g., sodiumthiosulphate.

A considerable number of chlorides will also have the desired effectwhen applied as aqueous solutions of the concentration range mentionedabove. Chlorides which give good results are those of magnesium,lithium, nickel, calcium, zinc, manganese, potassium and cobalt. In thecase of potassium chloride, a saturated solution should be used.

Liquid reagents and solutions of solid reagents in water are applied tothe brick after firing, as stated, by dipping, pouring or spraying afterwhich the treated brick are permitted to dry. They are then ready foruse. Dipping may conveniently be efiected by transporting the brick tothe furnace on a conveyor which travels for a portion of its length in astream of the treating solution. Liquid and solid reagents may also beheated to vaporization temperatureandihebrickpennitted .toabsorbthe staions-thereof. Liquid reagents and solid reagents in granular or powderedform may also be simply sprinkled on the brick as they are being laid.

In the cases Where the reagent is added to the mortar, the amountthereof should be between 3% and 10% of the wet mortar by weight. Thesolid reagent maybe used but preferably an aqueous solution of from 10to 30% concentration or even as high as 45 7a is used in lieu of water,to the desired amount, in making the mortar mix. The effect of thisprocedure is to cause diffusion of the reagent from the mortar into thebrick under the normal operating temperature of the brick when laid in afurnace lining. This diffusion also takes place from one brick toanother so it is not necessary that all the brick laid in a lining betreated. For example, treated brick may be laid alternately withuntreated brick. Whatever the details of the exact practice followed,the invention produces a furnace lining permeated with at least a traceof a reagent which inhibits disintegration as a result of carbondeposition.

Accelerated life tests on brick made .according .to the invention showconclusively that they will resist disintegration satisfactorily for thefull length of a normal furnace campaign and even longer. Such tests aremade by subjecting brick at a temperature of about 950 F. to anatmosphere of pure carbon monoxide. A life of forty hours under suchtest without serious disintegration has been determined by experience tosignify satisfactory serviceability of the brick in a furnace lining forthe length of the average campaign Brick treated in accordance with theinvention showed no noticeable disintegration after forty hours underthe accelerated life test.

If brick treated according to the invention be heated in an oxidizingatmosphere to a temperature over 1000 F., the-efiect-of.the-treatmentislargely destroyed but .the effect of the treatment remains after heatingto much higher temperatures in an atmosphere containing carbon monoxide.

Certain subject-matter disclosed herein but not claimed is claimed in mycopending applications Serial Nos. 251,825 and 251,826, filed October17, .1951.

I claim:

In a method of retarding disintegration of the lining of a blast-furnacecomposed of fire-clay'brick and mortar initially free of carbon, as aresult of the etfect of the carbon monoxide in the "furnace gases on theferric oxide in the fire clay 0f-which the brick and mortar comprisingthe lining are composed, the steps including treating one of saidcarbon-free lining materials with lithium chloride and then laying thebrick in the mortar in a blastfurnace to build up a lining therein.

Refenences .Cited infthe the .of this patent UNITED STATES PATENTS149,266 Swartout etal Mar. 31, .1874 182,935 .Kieran Oct. 3, 18761,285,244 Kunzler Nov. 19, 1918 1,585,826 Betts May 25, 1926 1,585,827Betts May 25, 1926 2,307,239 'Rowland Jan. 5, 1943 2,320,099 Ramseyetal. May 25, 1943 FOREIGN PATENTS 3,541 Great Britain of 1869 1,565 GreatBritain of 1899 3,501 Great Britain of 1867 2,883 Great Britain of 1856

